1. Field of the Invention
This invention relates to a method and apparatus for manufacturing K-files and reamers for use in performing root canals.
2. Background
K-type files and reamers are used in the field of endodontics to clean the root canals of human teeth for the purpose of removing organic material and extraneous material and for enlarging the root canal so that it may be filled.
Industry standards for K-type files and reamers are defined by the American Dental Association (ADA), International Standards Organization (ISO), and Federal-Military Specifications. As defined by these organizations, K-type files and reamers range in size from 0.6 mm to 140 mm, corresponding to the diameter of the tip, and range in length from 21 mm to 31 mm. The total number of spirals varies depending on the size of the instrument and whether the instrument is a K-type file or a reamer; the reamer having fewer number of spirals than K-type files. The overall length of the spiralled portion of each instrument is a minimum of 16 mm and the diametric taper is 0.02 mm change in diameter per mm in length (0.02 mm/mm).
These instruments are presently manufactured by one of the following three processes. In the first process, the feed stock is ground on three or four sides thereof in a tapered manner to form either a triangular or rectangular bar, depending upon whether a three fluted or four fluted instrument is being manufactured. That is, a tapered triangular bar is shaped for a three fluted instrument while a tapered rectangular bar is ground for a four fluted instrument. Thereafter, the triangular or rectangular tapered bar is twisted to provide a proper number of spirals as required by the industry standards. According to the first process, the grinding operation can encompass either a cross-feed flat grinding operation or a longitudinal feed flat grinding operation.
In the second process, the feed stock is initially ground to create a tapered cylindrical bar for the fluted portion of the instrument. Thereafter, flutes are individually ground on the tapered portion of the instrument to produce either a three or four fluted instrument, as required. This is accomplished by passing a rotating instrument, driven by a lead screw or similar device that produces the correct number of spirals, under a properly dressed grinding wheel thereby generating a flute. The instrument is then retracted, indexed 120.degree. or 90.degree. depending upon whether a three or four fluted instrument is being manufactured, and the process is repeated until each of the flutes are machined.
The third process involves grinding the taper and each of the flutes of the instrument simultaneously on an individual basis. This is accomplished by passing a rotating stock driven by a lead screw or similar device to produce the correct number of spirals under a properly dressed grinding wheel thereby generating a single flute. While the flute is being generated, either the rotating portion of the machine or the grinding wheel portion of the machine is translated such that the distance therebetween is continuously increased to create the proper taper. After the first flute is completed, the instrument is retracted, indexed 120.degree. or 90.degree. depending upon whether a three or four fluted piece is being manufactured, and the process is repeated for each flute.
As can be seen from the foregoing, each of these known processes require a long manufacturing time since each of the flutes are formed on an individual basis. Further, since the same portion of the grinding wheel is used to grind all the flutes, the life of the grinding wheel is relatively short.